Optical disk and optical disk drive device

ABSTRACT

In an optical disk having information recording tracks in the form of land and groove tracks, the disk is divided into a plurality of annular zones, each revolution of the information recording track belongs to one of the zones, and each revolution of the information recording track is divided into a plurality of sectors. A header portion is provided at the head of each sector and includes multiple recognition patterns which are each formed of a sequence of pits. A recognition pattern has a pattern which is not used as a pattern for data or addresses in the information recording part. The disk may be of a land/groove single-spiral configuration. The header portion for each sector may have a plurality of sub-headers, including an address of the sector, and first and second recognition patterns. The address of the sector and the first recognition pattern may be shifted in one radial direction by half a track pitch and the second recognition pattern shifted in the other radial direction by half a track pitch.

This application is a divisional of Applcation Ser. No. 09/182,492,filed on Oct. 30, 1998, now U.S. Pat. No. 6,069,869 which is adivisional of Application Ser. No. 08/747,607, filed on Nov. 13, 1996,now U.S. Pat. No. 5,867,474 the entire contents of which are herebyincorporated by reference.

BACKGROUND OF THE INVENTION

The present invention relates to an optical disk in which information isrecorded both on land and groove tracks.

The invention also relates to an optical disk drive device using such anoptical disk.

More particularly, the invention relates to recognition patterns usedfor recognition of the header part provided in front of each informationsector.

In conventional phase-change type optical disks, data is recorded onlyon grooves, and lands serve to guide the light spot for tracking, and toreduce crosstalk from adjacent groove tracks. If data is recorded onlands as well, the track density can be doubled on condition that thewidth of the grooves and the width of the lands are both unchanged. Ithas been discovered that the crosstalk between adjacent land and groovetracks is reduced if the difference in height between the lands andgrooves is λ/6 (λ being the wavelength of the light source). Because ofthis discovery, the use of both land and groove tracks has becomefeasible. The use of both land and groove tracks is also advantageouswith regard to the ease of mastering of the disk: it is easier to attaina certain recording density by the use of both land and groove tracksthan by reducing the track pitch using only the groove tracks.

For instance, in the case of optical disks for use as computer datafiles, optical disks in which data is recorded both on land and groovetracks, and the tracks are concentric, so that after recording of onerevolution (on a groove track, for example), a track jump is effected tostart writing on the adjacent track (a land track). Sectors are managedin accordance with the sector addresses. Accordingly, the operation forrecording and reproducing data, such as computer data, which need not becontinuous, can be carried out without difficulty.

Rewritable optical disks are however also used for recording continuousdata such as motion picture, or music. In multimedia applications (wherecomputer data and video and audio data are mixed), spiral tracks, as incompact disks, may be preferred because of the continuity of the tracks.

In this case, the tracks need to be formed into a spiral form ratherthan a concentric form. However, in an optical disk in which theinformation is recorded both on lands and grooves and the tracks arespiral, it is necessary, after tracing the entire spiral formed of allthe land tracks, for example, and groove tracks, to jump from the end ofthe land track spiral to the beginning of the groove track spiral. It isthen necessary to access from the inner periphery to the outer peripheryof the disk. Such an operation is time-consuming. In a disk which isdivided into annular zones, the track jump is made from the innerperiphery of the zone to the outer periphery of the zone, and the timefor the jump is shortened but there is still a similar problem.

FIG. 23A and FIG. 23B show details of the header region 4 in aconventional optical disk wherein data is recorded on both groove andland tracks. FIG. 23A shows the case where headers are providedseparately for the land and groove tracks, and addresses dedicated tothe respective tracks are formed. FIG. 23B shows the case where headersare provided on an extension of a boundary between land and groovetracks, and each address is shared by the land track and the groovetrack separated by the boundary. In either case, the headers includeaddress pits.

The header portion is formed of embossments (dents or projections)physically formed for representing the address information and the likeof the sector preceded by the header, the sector being a unit forrecording data. Specifically, pits having the same height as the lands,or pits having the same depth as the grooves are formed in the headerportion where no tracks are formed.

There are several methods for forming prepits suitable for theland/groove recording configuration. Two principal ones are those shownin FIG. 23A and FIG. 23B.

In the configuration shown in FIG. 23A, dedicated prepits are providedfor each sector of the land or groove track. Because the dedicatedprepits can record various items of information, such as the oneindicating whether the sector following the dedicated prepits is in aland track or a groove track, control in the optical disk drive deviceis facilitated. However, the width of the prepits must be sufficientlynarrower than the track width. This means that the laser beam used forforming the tracks cannot be used for forming the prepits, and thefabrication of the medium is difficult.

In the configuration shown in FIG. 23B, the prepits are shared by theland and groove tracks adjacent to each other. The prepits can be formedby using the same laser beam as that used for forming the tracks, and byshifting the laser beam by ½ of the track pitch laterally of the track,i.e., in the radial direction of the disk. However, during writing orreading of the disk, the shared prepits cannot indicate whether thesector following the prepits is in a land track or groove track, so thatthe optical disk drive device must have a means to find whether a landtrack or groove track is being traced by the light spot, and the controlin the optical disk drive device is difficult.

In the above-described optical disk allowing recording and reproduction,it is also necessary to solve the problem of the track offset. Thisrelates to the fact that the one beam-and-push-pull method is used forthe tracking, rather than a three-beam method. This is because therecording requires a greater laser power. Also, in the case ofpit-forming recording, such as the one on a write-once disk, the sidespots (used in a three-beam method) causes a disturbance to the trackingoperation.

In a push-pull tracking, the tracking error is detected using thediffraction distribution of the light spot illuminating the pregroovesas shown in FIG. 24, and fed to the servo system, so that offset mayoccur due to the eccentricity of the disk or tilting of the disk. Moreparticularly, an optical head 10 has a laser diode 66 emitting a laserbeam, which is passed through a half-mirror 65 and an objective lens 67to illuminate an optical disk 8 rotated by a disk motor 9. The reflectedlight beam from the light spot on the disk 8 is guided by the objectivelens 67 and the half-mirror 65 and is received by a photodetector 11,and the tracking error is detected using the diffraction distribution ofthe light spot on the optical disk 8. The detected tracking error isused to control an actuator coil 64 for driving the objective lens 67.

For instance, a tilt of 0.7 degrees or an eccentricity of a 100 μm(equivalent to lateral movement of the objective lens 62 of 100 μm asindicated by broken lines in FIG. 24) causes shifting of a lightdistribution 12 on the photodetector 11, and hence an offset of 0.1μ.

To prevent such a phenomenon, a drive device having higher mechanicaland optical accuracy is used, and various other contrivances areadopted.

FIG. 25A shows the method of mirror surface correction in which a mirrorsurface part 7 is used. FIG. 25B shows the pit configuration of theoptical disk used in combination with the wobble pits correction method.

In this method, wobble pit pits 68 and 69 being shifted in the radialdirection of the disk by ½ of the track pitch are used. These methodsare described in the following publications:

(1) Ohtake, et al. “Composite Wobbled Tracking in the Optical DiskSystem,” on pp. 181-188 in Optical Memory Symposium '85, held on Dec.12-13 in 1985, published by Optical Industry Technology PromotionAssociation,

(2) Kaku, et al. on “Investigation of compensation method for trackoffset,” pp. 209-214 in Optical Memory Symposium '85, held on Dec. 12-13in 1985, published by Optical Industry Technology Promotion Association.

FIG. 26 shows a track offset correction circuit used in combination witha disk having the mirror surface portion 7 shown in FIG. 25A. A splitphotodetector 70 detects the tracking error by a push-pull method. Anadder 15 adds the outputs of the two half-portions of the splitphotodetector 70 to produce a signal indicative of the total amount oflight received, which corresponds to the total amount of light reflectedfrom the disk. A differential amplifier 16 determines the differencebetween the outputs of the two half-portions of the split photodetector70, to produce a signal indicative of the tracking error. A mirrorsurface detector 20 detects the mirror surface portion 7. A sample-holdcircuit 23 samples and holds the tracking error signal when the lightspot passes the mirror surface portion 7, and holds the sampled value asan offset information. A differential amplifier 47 determines thedifference between the tracking error signal and the offset information.The output of the differential amplifier 47 indicates the tracking errorhaving the offset removed.

FIG. 27 shows an offset correction circuit used in combination with adisk having wobble pits shown in FIG. 25B. A wobble pit detector 22receives the output of the adder 15, and detects the wobble pits, i.e.,produces a signal to a sample-hold circuit 23 when the light spot passesthe wobble pit laterally shifted toward one side of the track, andproduces another signal to a sample-hold circuit 24 when the light spotpasses the wobble pit laterally shifted toward the other side of thetrack. Responsive to these signals (i.e., when the light spot passes thewobble pits 68 and 69), the sample-hold circuits 23 and 24 sample theoutput of the differential amplifier 16, and holds the sampled value. Adifferential amplifier 27 determines the difference between the outputsof the sample hold circuits 23 and 24, as an offset. An adder 28 addsthe tracking error signal obtained at the differential amplifier 27 tothe tracking error signal obtained by means of the ordinary push-pullmethod, to produce the tracking error signal from which the offset hasbeen removed.

FIG. 28 illustrates the control characteristics for the case where atracking error signal obtained by wobble pits and the tracking errorsignal by means of the conventional push-pull method are both used. G1denotes a tracking open loop characteristic by means of the conventionalpush-pull method, and G2 denotes a tracking open loop characteristic bymeans of the wobble pits.

In this configuration, the guide grooves are discontinuous orinterrupted at the mirror surface portion 7. With this configuration, acorrection circuit for correcting the mirror surface offset, shown inFIG. 26, is required. The signals output from the two half-portions ofthe split photodetector 70 are input to the differential amplifier 16,which thereby produces a tracking error signal. The sum signal producedby the adder 15 is supplied to the mirror surface detector 20, whichthereby generates a timing signal indicating the timing at which thelight beam passes the mirror surface portion, and hence the signalshould be sampled. The tracking error signal ΔT produced by thedifferential amplifier 16 includes an error component ΔTg (error due tothe photodetector 70 and the differential amplifier 16), a true trackingerror ΔTs, and an offset component δ due to various causes including thetilting of the disk, so that it is given by:

ΔT=ΔTs+ΔTg+δ  (1)

The sample-hold circuit 23 samples the tracking signal at the mirrorsurface portion 7, and holds the sampled value for each sector. Theoutput of the sample-hold circuit 23 represents ΔTg+δ. Accordingly, inview of the equation (1), subtracting the output of the sample-holdcircuit 23 from the output of the differential amplifier 16 at thedifferential amplifier 47 results in the true tracking signal ΔTs. Inthis way, a closed-loop servo system for achieving an accurate trackfollowing can be formed.

Another method of correction is a method using wobble pits. According tothis method, a pair of sequences of pits shown in FIG. 25B are formed byalternately deflecting the light beam, using ultrasonic deflector,during fabrication of the original disk for mastering. During recordingand reproduction, the amounts of the reflected light received when thelight spot is passing the wobble pits on the respective sides arecompared, to detect the tracking error. Specifically, a differentialamplifier 27 shown in FIG. 27 determines the difference between theoutputs of the sample-hold circuits 23 and 24 to obtain the trackingerror. As shown in FIG. FIG. 29, when the light spot passes along a linecloser to the center of the pit 68 on one side (top side in FIG. 25B)than to the center of the pit 69 on the other side (bottom side in FIG.25B), an output signal illustrated by the dotted line is obtained. Whenthe light spot passes along a line closer to the center of the pit 69 onthe bottom side than to the center of the pit 68 on the top side, anoutput signal illustrated by the solid line is obtained. The differenceobtained by subtracting the signal (amount of received reflected light)obtained when the light spot is passing the wobble pit 69 at the back,from the signal (amount of received reflected light) obtained when thelight spot is passing the wobble pit 68 at the front, represents themagnitude of the tracking error and the direction of the tracking error.This means that the position at which the light spot passes is detected.Compared with the method relying on the diffraction distribution due topre-grooves, the above-described method realizes a better servo system.

Another tracking method has been proposed, in which the feature of theabove-described wobble pit method is maintained, and which is compatiblewith systems using conventional push-pull tracking method. The sectorconfiguration in this system is composed of an index field with pre-pitsshown in FIG. 23B, and data field which the user later utilizes. Theindex field is provided with address information, as well as wobble pitswhich may or may not serve also as a sector detection mark, andpre-grooves for tracking.

With such a configuration, the true tracking error is detected from thewobble pits, and the offset used in the push-pull tracking can becorrected. In this case, the open-loop characteristic of the trackingservo is such that the gain for tracking on the basis of the wobble pitsis relatively large in the low-frequency region, and the gain for thetracking on the basis of the push-pull method is relatively large in thehigh-frequency region, as shown in FIG. 28. As a result, data can berecorded and reproduced, while the light spot is maintained on thecenter of the track, regardless of the drive device used, andcompatibility between the recorded disk and the drive device can bepreserved.

With the above-described optical disk drive device, information isrecorded on lands and grooves to increase the recording density. In suchan optical disk, to avoid the complexity of operation duringdisk-mastering, it was necessary to provide address pits in the headerportion, being ½ pitch shifted in the radial direction from theinformation track, so as to enable reading during tracing of the landtrack or groove track. Each header is therefore shared by the land andgroove, whether the light spot is scanning a land or a groove is notknown from the address alone.

The sequences of pits for recording the address information are disposedat positions shifted with respect to the track center, so that when thesignal amplitude is lowered or track offset occurs, it is difficult toobtain information reliably. In particular, when the address informationis incorrectly read, the recording and reproduction of information overthe entire sector cannot be achieved, and fundamental information as towhether the light spot is scanning a land or a groove, or in which zonethe light spot is scanning, or the like may become incorrect, and thedisk rotation control, tracking control, or the like may fail.

In the case of a disk of a spiral configuration in which a land and agroove alternate every revolution, it is necessary to judge whether thesector following the header is in a land or a groove. This judgment mustbe reliable, since if this judgment is erroneous, failure of trackingmay occur.

Furthermore, because the tracking polarity is reversed every revolution,the polarity of the tracking error signal is reversed every revolution,and error in counting using the tracking error signal during trackaccess, or failure in pull-in at the time of track jump may occur.

In addition, during access, when the boundary between adjacent zones isnot known, CLV (constant linear velocity) control is effected aftertracking onto the target track, so that the settling requires time. Toavoid this problem, a detecting means which can detect the trackingpolarity and the current zone position even when tracking is notattained.

SUMMARY OF THE INVENTION

The present invention has been achieved to solve the problems describedabove, and its first object is to provide an optical disk in whichrecording can be made on both of lands and grooves, and havingrecognition patterns in the headers for the information sectors, whichcan be distinguished clearly from recorded data, and which permitsreliable detection with an error rate lower than recorded data.

A second object is to provide recognition patterns in the headers whichenable identification of the zone to which the sector belongs, andjudgment as to whether the sector is in a land or a groove.

A third object is to provide an optical disk and an optical diskreproducing device by which the recognition patterns in the headers canbe decoded even when tracking is not achieved, and disk rotation controlcan be achieved during access.

A fourth object is to provide an optical disk and an optical diskreproducing device by which the recognition patterns in the headers canbe reproduced and decoded even when tracking is not achieved, and thetrack count error during access can be reduced, and stable pull-inoperation to the target track is enabled.

According to one aspect of the invention, there is provided an opticaldisk having information recording tracks in the form of land and groovetracks, the disk being divided into a plurality of annular zones, eachrevolution of the information recording track belonging to one of thezones depending on the position in the radial direction of the track,

each revolution of the information recording track being divided into aplurality of sectors of a unit length of information recording in thedirection of the scanning,

the disk having a header portion at the head of each sector,

the header portion including a recognition pattern which is formed of asequence of pits having a pattern which is not used as a pattern fordata or address in the information recording part, in the modulationmethod used.

The disk may be of a land/groove single-spiral configuration in whichland tracks and groove tracks are connected at connecting points,occurring every revolution, so that land and groove tracks alternateevery revolution along a continuous spiral.

It may be so arranged that the header portion for each sector has aplurality of sub-headers, including an address of the sector, and firstand second recognition patterns,

major part of the sub-headers including the address of the sector, andthe first recognition pattern are provided, being shifted in one radialdirection by half a track pitch with respect to the center of the trackof the sector, the second recognition pattern being provided beingshifted in the other radial direction by half a track pitch with respectto the center of the track of the sector.

With the above arrangement, sequences of information which are notincluded in the modulation patterns used for the information recordingare used for the recognition patterns. The pattern matching duringreproduction of the recognition patterns can be effected reliably, andreliable discrimination between the recognition patterns and recordingdata can be made. Furthermore, a plurality of subheaders including apair of recognition patterns and the address of the sector are disposed,with the first one of the recognition patterns and the address beingshifted by half a track pitch in one lateral direction, with the otherrecognition pattern being shifted in the other lateral direction.Accordingly, they can be used for detection of track offset, andproviding the plurality of pairs of recognition patterns enablescomparison, and prevents erroneous detection.

The recognition patterns used for determining the timing of detection ofthe address data, and timing of detection of wobble pits (formed of thesubheaders for the sector which is scanned after the header, and thesubheaders for the sector in the next track) and mirror surface part areof a sequence of pits having a pattern which is not used for informationrecording. As a result, judgment as to whether the reproduced signalrepresents a recognition pattern or the recorded information can be madereliably. The detection of the address data and tracking offset can bemade reliably, and the tracking operation free from offset can beachieved.

A mirror surface part may be provided at the back of the recognitionpattern.

The recognition pattern may be formed of pits of different lengths, theminimum length being longer than the minimum pit length of the signal ofthe data recorded in the information recording part.

With the above arrangement, the information for the recognition patternscan be reproduced even in a state of track deviation.

Also, even when the reproducing spot size is enlarged due to defocusing,because of vibration of the device, for instance, information can bereproduced with a low error rate, and the stability in the offsetcorrection operation and polarity reversal operation is improved.

The recognition patterns in the header may contain an identificationcode indicating the zone to which the sector belongs.

With the above arrangement, the identification of the zone can be madenot only during recording and reproduction of information, but alsoduring track access. Specifically, such identification of the zone canbe made even at the time of the servo pull-in when the trackingoperation is not yet stable, and when the tracking servo is not applied,during track access.

The recognition patterns in the header may contain an identificationcode indicating whether the information recording part of the sector isa land or a groove.

With the above arrangement, the identification as to whether the sectoris a land or a groove can be made not only during information recordingand reproduction, but also during track access.

As a result, in a disk in which the land and groove alternate everyrevolution to form a continuous track, a continuous track crossingsignal, similar to that obtained with the prior art spiral disk, can beobtained.

The headers may be aligned in the radial direction, and the intervalbetween the recognition patterns may be varied.

The interval between the recognition patterns may be varied by varyingthe length of the VFO.

According to another aspect of the invention, there is provided anoptical disk drive device using an optical disk having informationrecording tracks in the form of land and groove tracks, the disk beingdivided into a plurality of annular zones, each revolution of theinformation recording track belonging to one of the zones depending onthe position in the radial direction of the track,

each revolution of the information recording track being divided into aplurality of sectors of a unit length of information recording in thedirection of the scanning,

the disk having a header portion at the head of each sector,

the header portion including a recognition pattern which is formed of asequence of pits having a pattern which is not used as a pattern fordata or address in the information recording part, in the modulationmethod used,

the device comprising:

means for generating a light spot and causing the light spot to scanalong the track;

means for receiving light reflected from the disk;

means for detecting the amount of reflected light; and

a pattern matching circuit responsive to the means for detecting theamount of reflected light, for detecting the recognition pattern.

According to a further aspect of the invention, there is provided anoptical disk drive device using an optical disk in which the informationrecording tracks are present both on lands and grooves, and the diskbeing divided into a plurality of annular zones, the disk having anidentification code in each header indicating the zone to which theheader belongs,

the device comprising:

means for generating a light spot and causing the light spot to scanalong the track;

means for receiving light reflected from the disk;

means for reproducing a signal based on the reflected light;

means for reading said identification code from the reproduced signalduring track crossing, during track access or when the tracking servo isnot operating; and

means for controlling the rotational speed of the optical disk on thebasis of the result of the reading.

During track access or when the tracking servo is not operating, therecognition pattern can be reproduced from the reproduced signal duringtrack crossing, and the rotational speed of the optical disk can becontrolled on the basis of the result of the reproduced identificationcode.

As a result, the settling of the motor can be accomplished promptly, andthe access time can be shortened in a disk of zone CLV system. Inparticular, with a phase-change type disk, the recording depends of thelinear speed. By shortening the settling time, the average datarecording rate can be improved.

According to a further aspect of the invention, there is provided anoptical disk drive device using an optical disk in which land and groovetracks alternate every revolution to form a continuous informationtrack, and the disk being divided into a plurality of annular zones,

the disk having recognition patterns including an identification codeindicating whether the header is at a connecting point between a landand a groove,

the device comprising:

means for generating a light spot and causing the light spot to scanalong the track;

means for receiving light reflected from the disk;

means for reproducing a signal based on the reflected light;

means for reading the identification code from the reproduced signalduring track crossing, when the track servo is not operating, and

means for performing track pull-in after switching the polarity of thetracking error signal on the basis of the reading.

With the above arrangement, the track pull-in operation in a disk havingalternating lands and grooves is facilitated.

That is, erroneous pull-in to an adjacent track due to the difference inthe polarity can be prevented, and the access to the target address canbe achieved accurately.

According to a further aspect of the invention, there is provided anoptical disk drive device using an optical disk in which lands andgrooves alternate every revolution to form a continuous informationtrack, and the disk being divided into a plurality of annular zones,

the said disk having recognition patterns including an identificationcode indicating whether the header is at a connecting point between aland and a groove,

the said device comprising:

means for generating a light spot and causing the light spot to scanalong the track;

means for receiving light reflected from the disk;

means for reproducing a signal based on the reflected light;

means for reading the identification code from the reproduced signalduring track access, and

means for performing track count from the tracking error signal, afterswitching the polarity of the tracking error signal on the basis of thereading.

With the above arrangement, continuous track crossing signal isobtained, and the count error (especially, during a high-speed access)is reduced.

According to a further aspect of the invention, there is provided anoptical disk drive device using an optical disk having informationrecording tracks in the form of land and groove tracks, the disk beingdivided into a plurality of annular zones, each revolution of saidinformation recording track belonging to one of the zones depending onthe position in the radial direction of the track,

each revolution of the information recording track being divided into aplurality of sectors of a unit length of information recording in thedirection of the scanning,

the disk having a header portion at the head of each sector,

the header portion including a recognition pattern which is formed of asequence of pits having a pattern which is not used as a pattern fordata or address in the information recording part, in the modulationmethod used,

the header further including a VFO,

the device comprising:

means for generating a light spot and causing the light spot to scanalong the track;

means for receiving light reflected from the disk;

means for reproducing a signal based on the reflected light;

means responsive to the reproduced signal corresponding to the VFO, forgenerating PLL clock pulses;

means for counting the clock pulses; and

means for responsive to the result of the counting, for outputting asignal at a timing at which the light spot scans the wobbling addresspits, or the mirror surface part.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows a disk having land and groove tracks forming separatespirals.

FIG. 1B shows disk a single spiral formed of land and groove tracksalternating every revolution.

FIG. 2 shows how the zones are configured.

FIG. 3A shows the configuration of the pits in the header region.

FIG. 3B shows the disposition of the address pits in the header region.

FIG. 4 is a block diagram showing a part of an optical disk drive deviceconcerning the tracking error signal offset correction using wobblepints and mirror surface parts, according to Embodiment 1.

FIG. 5 shows the arrangement of the pits in the header part of theoptical disk of Embodiment 1.

FIG. 6 shows the recognition patterns in the optical disk of Embodiment1.

FIG. 7A to FIG. 7C show examples of recognition patterns in an opticaldisk of Embodiment 1.

FIG. 8 shows the pit configurations of the recognition patterns in anoptical disk of Embodiment 1.

FIG. 9 shows the configuration of the recognition patterns in an opticaldisk of Embodiment 1.

FIG. 10 shows the details of the recognition patterns in an optical diskof Embodiment 1.

FIG. 11 shows a recognition pattern formed of 4 bytes, in an opticaldisk of Embodiment 1.

FIG. 12 shows a recognition pattern formed of 3 bytes, in an opticaldisk of Embodiment 1.

FIG. 13 shows a recognition pattern formed of 2 bytes, in an opticaldisk of Embodiment 1.

FIG. 14 shows the recognition patterns and the traces of the light spotduring track crossing, according to Embodiment 2.

FIG. 15A shows another example of recognition patterns disposed atvarying interval, and the traces of the light spot during trackcrossing, according to Embodiment 2.

FIG. 15B shows a further example of recognition patterns disposed atvarying interval, and the traces of the light spot during trackcrossing, according to Embodiment 2.

FIG. 16 shows signals during the track crossing according to Embodiment2.

FIG. 17 is a block diagram showing a system for controlling rotationduring track crossing according to Embodiment 2.

FIG. 18 is a block diagram showing a system for polarity reversal andtrack counting during track crossing according to Embodiment 2.

FIG. 19 is block diagram showing a pattern matching for the recognitionpatterns in an optical disk drive device according to Embodiment 2.

FIG. 20 is block diagram showing a pattern matching for the recognitionpatterns, in which matching of the ID is also applied.

FIG. 21 is block diagram showing a pattern matching using therecognition patterns on one side only.

FIG. 22 is a block diagram showing a pattern matching using therecognition patterns on one side only, and offset correction.

FIG. 23A and FIG. 23B show header parts in an optical head in the priorart.

FIG. 24 shows how the offset is generated in the optical head.

FIG. 25A and FIG. 25B show a mirror surface and wobble pits in anconventional optical disk.

FIG. 26 is a block diagram showing a part of a conventional optical diskdrive device concerning the tracking error signal offset correctionusing mirror surface parts.

FIG. 27 is a block diagram showing a part of a conventional optical diskdrive device concerning the tracking error signal offset correctionusing wobble pits.

FIG. 28 shows control characteristics of the conventional. optical diskdrive using wobble pits and push-puss method.

FIG. 29 is a diagram showing waveforms of the outputs obtained from thewobble pits.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the invention will now be described with reference to thedrawings.

Embodiment 1

Examples of the overall configuration of the disk of this embodiment areshown in FIG. 1A and FIG. 1B. The example shown in FIG. 1A is an opticaldisk in which all the lands 2 form a single continuous spiral and allthe grooves 1 form a separate continuous spiral. The tracks are dividedinto sectors 3, by header regions 4.

The example shown in FIG. 1B is an optical disk in which lands 2 andgrooves 1 alternate every revolution, so that all the grooves 1 andlands 2 in combination form a single continuous spiral. The tracks aredivided into sectors 3 by header regions 4 a or 4 b. The header regions4 a are at a connecting point where the lands and grooves are connectedwith each other. The header regions 4 b are not at a connecting point.

FIG. 2 shows the arrangement of the zones in the optical disk ofEmbodiment 1. The optical disk is shown to be divided into three zonesZ-A, Z-B and Z-C.

The configuration of the header regions 4 in FIG. 1A (or the headerregions 4 b in FIG. 1B) which are not at the connecting point areillustrated in FIG. 3A and FIG. 3B. Specifically, FIG. 3A shows anarrangement of pits, and FIG. 3B shows an arrangement of address data.

The header in each header region is associated with the sector followingthe header. In the example shown in FIG. 1A and FIG. 1B, there are 8sectors per revolution. In an actual design of an optical disk, thereare tens of sectors per revolution.

A groove track 1 a (one of the groove tracks 1, but denoted by 1 a fordistinction from other groove tracks 1) is interrupted by the headerregion (4 or 4). That is, the groove track 1 a on one side (e.g., to theleft of the header region in FIG. 3A) and the groove track 1 a on theother side (to the right of the header region) are aligned with eachother, and the light spot having passed the groove track 1 a on theleft, crosses the header region 4, and then traces the groove track 1 aon the right.

Two subheaders 5 a in the header region 4 each include a sequence ofaddress pits 31 a which indicates the address of the sector in thegroove track 1 a following the header region 4 and is shifted in a firstdirection lateral of the groove track 1 a, i.e., radially inward (orupward in FIG. 3A) by half a track pitch (a full track pitch being thedistance between the land and groove tracks adjacent to each other). Twosubheaders 5 b in the header region 4 each includes a sequence ofaddress pits 31 b which indicates the address of the sector in the landtrack 2 b following the header region 4 and is shifted in the same,first direction lateral of the land track 2 b, i.e., radially inward (orupward in FIG. 3A) by half a track pitch.

The subheaders 5 a and 5 b including the address pits 31 a and 31 b,respectively, for the sectors in the groove and land tracks, followingthe header region are shifted with respect to each other in thedirection of the track, so that they do not overlap in the radialdirection.

Because the address pits (31 a and 31 b, for example) for the sectors ongroove and land tracks 1 a and 2 b adjacent to each other are notoverlapped with each other, the pitch of the address pits in the radialdirection is twice the track pitch. The address pits may therefore havethe same width as the land or groove tracks, so that the address pitscan be formed using the same laser beam as that used for forming theland or groove tracks.

The combination of the sequences of pits in the subheaders shifted inalternate directions are also called wobble pits, and serve to provideinformation indicating the tracking error, as will be described later.

The value or contents of the respective groups or sequences of addresspits in the respective subheaders are as shown in FIG. 3B.

In the example shown in FIG. 3B, the same address value (e.g., any of“A,” “B,” “C,” and “D”) is repeated twice. That is, the address isduplexed. The same address sector (e.g., A) is represented by theaddress pits shifted in one direction. Different addresses (e.g., “A”and “B”) alternate.

A mirror surface part 7 is a part where no lands and grooves are formed.In other words, grooves and lands are interrupted at the mirror part,and is used for track offset.

In the case of the disk shown in FIG. 1B, at the header regions 4 awhich are at the connecting points, polarity of the tracking error mustbe reversed, while at the remaining header regions 4 b, the trackingpolarity need not be reversed.

FIG. 4 shows a system in which correction of offset due to polarityreversal is effected by the mirror surface detection method, while thesensor offset due to the conventional push-pull method is corrected bythe wobble pits. The illustrated system includes a disk motor 9 forrotating an optical disk 8.

Light reflected from an on optical disk 8 is received by a trackingsensor 11, in the form of a split photodetector, provided in an opticalhead 10. The tracking sensor 11 is illustrated to be outside of theoptical head 10, but it is actually within the optical head 10. Atypical distribution of light received by the tracking sensor 11 is alsoillustrated by a curve 12. I-V amplifiers 13 convert the photo-currentsoutput from the respective half portions of the tracking sensor 11, intovoltage signals. A polarity reversing circuit 14 reverses the trackingpolarity, i.e., the polarity of the tracking error signal. An addingamplifier 15 determines the amount of light reflected from the opticaldisk 8. A differential amplifier 16 determines the difference of theoutputs of the two half portions of the tracking sensor 11, called E andF channels of the tracking sensor 11.

A PLL and data detecting circuit 17 extracts data from the output of theadding amplifier 15. A pattern matching circuit 18 performs patternmatching, including the pattern matching of the wobble pits.

A connecting point detecting circuit 19 determines whether the headerregion being scanned is at a connecting point, and hence whetherpolarity reversal is to be effected. A mirror surface detecting circuit20 detects the mirror surface part 7 formed on the optical disk 8.

A wobble pit detecting circuit 22 detects the wobble pits, and producesa first signal when the light spot is passing the first sequence ofaddress pits shifted in one direction, and a second signal when thelight spot is scanning a second sequence of address pits, next to thefirst sequence, shifted to the other direction.

A sample-hold circuit 23 samples the tracking error signal when thelight spot is found to be passing a mirror surface part 7, and when theheader is found to be at a connecting point, and holds the sampled valueuntil the next sampling.

A differential amplifier 26 subtracts the output of the sample-holdcircuit 23 from the output of the differential amplifier 16 to removethe offset in the tracking error signal.

A sample-hold circuit 24 samples the output of the adder 15 when whenthe light spot is scanning the sequence of address pits shifted in onedirection.

A sample-hold circuit 25 samples the output of the adder 15 when thelight spot is scanning the sequence of address pits shifted in the otherdirection.

A differential amplifier 27 determines the difference between theoutputs of the sample-hold circuits 24 and 25. An adder 28 adds thetracking error signal generated by the wobble pits to the originaltracking error signal.

FIG. 5 shows the details of the configuration of the pits in the headerpart in the optical disk of Embodiment 1. It contains VFO 29 forfacilitating PLL pull-in, and detection of the address or the like inthe header part, recognition patterns 30 for recognition of the header,and address data 31 indicating the address number of the sector.

FIG. 6 shows the pit configuration of a plurality of sub-headers 5 inthe header part 4 in the optical disk of Embodiment 1.

FIG. 7A to FIG. 7C show examples of configurations of the recognitionpatterns 30 in the header part in the optical disk of Embodiment 1.

FIG. 8 shows the VFO 29 and recognition pattern 30 in the header part inthe optical disk of Embodiment 1, and scanning trace of the light spotLS during track access.

FIG. 9 shows the configuration of the sub-header 5 in the header part inthe optical disk of Embodiment 1. It includes a VFO 29, recognitionpatterns (RP) 30 and address data 31.

FIG. 10 shows the configuration of the recognition patterns 30 in thesub-header 5. It includes matching pits 32, an ID 33 describing theorder of the matching pattern within the subheader, zone identifyingpart 34 indicating the zone to which the header belongs, and a mirrorsurface 35 for offset correction.

FIG. 11 shows an example of the recognition pattern 30 formed of 4bytes.

FIG. 12 shows an example of the recognition pattern 30 formed of 3bytes.

FIG. 13 shows an example of the recognition pattern 30 formed of 2bytes.

As will be seen from FIG. to FIG. 13, the recognition patterns 30 ineach subheader 5 are provided in pairs, and one of the recognitionpatterns in each pair is shifted from the rest of the pits in thesubheader in the radially outward direction (downward in the drawings)by a track pitch. The reason for this will be described later

In a land/groove disk shown in FIG. 1A, the land track 2 and groovetrack 1 form separate spirals. That is, one of the two spirals is formedonly of lands 2 and the other spiral is formed only of grooves 1. Incontrast, in an optical disk shown in FIG. 1B, a single continuousinformation track is formed by alternating the lands and grooves everyrevolution, so that each revolution of land is connected to another,adjacent revolution of groove, which in turn is connected an adjacentrevolution of land, and so on.

In the optical disk shown in FIG. 1B, data is recorded along a singlespiral track, as in CD (compact disk), so that track jump can beeffected in the same way as in CD. In the optical disk shown in FIG. 1A,it is necessary that, after scanning all the way through one of the twocontinuous tracks, to jump from the tail end of said one of the twospiral tracks to the leading end of the other spiral track, and therecording rate is lowered at this point. An advantage, however is that,when forming a track by the use of a mastering device, tracing a simplespiral is adequate.

In the fabrication of the optical disk shown in FIG. 1B, the laser beammust be shifted in the radial direction by a track pitch, everyrevolution. A more serious problem is that it is necessary to switch thetracking error signal polarity every revolution, between that for landsand that for grooves, and offset associated with the polarity switchingis problematical.

Moreover, with an optical disk for recording and reproduction, thelinear speed is maintained constant by the used of the CLV (constantlinear velocity), or variation in the linear speed is reduced by amethod in which the disk is divided into several annular zones and therotational speed speed is varied from one zone to another. In the caseof the CLV rotation, the header parts for the respective sectors are notaligned in the radial direction, so that crosstalk interference from theprepits in the header part can be a problem. Accordingly, in general,the disk of the zone configuration shown in FIG. 2 is employed.

The configuration of the header part for each sector is such that, asshown in FIG. 3, the sub-headers are recorded radially shiftedalternately by half a track pitch, so that separate addresses can bereproduced for the land and groove.

With the conventional address pit configuration shown in FIG. 23A, alaser beam having an intensity different from that used for forming thegrooves must be used for forming the pits in the headers. In the case ofthe configuration shown in FIG. 23B, the same address is reproducedduring scanning of a land and a scanning of an adjacent groove, so thatthe it is not possible to determine, from the reproduced signal alone,whether the light spot is scanning a land or a groove.

With the configuration shown in FIG. 3 according to Embodiment 1, theaddress pits for the lands and grooves following the header parts areshifted in different radial directions, by half a track pitch, and beingshifted also in the direction of the track, so that the address for theland and the address for the groove appear sequentially and in differentradial directions with respect to the scanning movement of the lightspot, so that it is possible to determine the address for the sector ineach track from the reproduced data. For instance, when the groove track1 a is being scanned, the addresses are reproduced in the order ofaddress A, address B, address A and address B. When the land track 2 bis scanned, the addresses are reproduced in the order of address C,address B, address C and address B. From such a difference, and it ispossible to determine whether the sector following the header region isin a groove track or a land track.

The address pits are disposed to form wobbling pits, and the mirrorsurface part 7 is provided, so that it is possible to remove theunnecessary offset of the push-pull sensor system, due to the shiftingof the objective lens and the tilting of the disk.

Methods of removing offset which are known in the art includes mirrorsurface correction and wobble pit correction. In a usual optical diskcapable of recording and reproduction, the configuration in which thegroove is not provided at a specific location is formed by formingheader parts for the sectors, and the information such as sector addressand the like is written as embossed pits in advance. In the case ofland/groove recording, if the embossed pits are formed as shown in FIG.3, the address pits themselves can be used as wobble pits.

A problem associated with an optical disk in which lands and groovesalternate every revolution as shown in FIG. 1B, is that there is oneheader 4 a per revolution where the tracking polarity must be switched.

The tracking error signal ΔT immediately before a servo compensationcircuit, obtained in a push-pull method is given by the followingequation:

ΔT=ΔTs+ΔTg+δ+ΔTt+ΔTi+ΔTh  (2)

where

ΔTs is a true tracking error signal;

ΔTg is an offset due to the shift of the objective lens;

δ is an offset due to the tilting of the disk;

ΔTt is an offset due to mounting error of the optical detector and straylight in the optical head;

ΔTi is an offset from the detector to the polarity reversing circuit;and

ΔTh is an offset from the polarity reversing circuit to the compensationcircuit in a servo system.

The polarity of the true tracking error signal ΔTs is reversed each timethe track is changed from a land to a groove, or from a groove to aland. By reversing the polarity by the polarity reversing circuit 14, acorrect track error signal can be obtained. Thus, the polarity reversaldoes no produce any problem with regard to ΔTs. On the other hand, theoffset ΔTg due to the shift of the lens, or the offset δ due to thetiling of the disk occur independently of whether the light spot isscanning a land or a groove. If the polarity of the tracking errorsignal were reversed without taking the above in consideration, thereverse offset would be applied. It is thus necessary to alter or updatethe amount of correction for the offset components ΔTg and δ obtained bythe wobble pit method or mirror surface method.

In a method using ΔTg calculated from the objective lens position sensorof the optical head, or a method for correcting after storing ΔTg in amemory for one revolution of the track prior to tracking operation,correction will be made without reversing the polarity of ΔTg at thetime of tracking error signal polarity reversal.

With regard to ΔTt and ΔTi, it is sufficient if the amounts ofcorrection are determined before the device is used for operation, orwhen the device is shipped from the manufacturer, so that these offsetsas well as ΔTh, are in many cases, corrected by the offset adjustmentand the like of the servo circuit. However, while the polarities of ΔTtand ΔTi are reversed at the time of tracking error signal polarityreversal, ΔTh is not reversed. As a result, an offset error of ΔTt andΔTi in the reverse direction may be created. For this reason, as shownin FIG. 4, the sample-hold circuit 23 is provided at the back of thepolarity reversing circuit 14 to sample and hold the tracking errorsignal at the time when the light spot passes the mirror surface part 7,and on the basis of the output of the sample-hold circuit 23, theoriginal tracking error signal (tracking error signal as output from thedifferential amplifier 16) is corrected by the differential amplifier26. In this way, the correction of the offset, including ΔTt and ΔTi canbe achieved.

By providing the sample-hold circuit 23 dedicated to the tracking errorsignal polarity reversal, as shown in FIG. 4, even when the address pitsor the recognition flag for the sector at the connecting point is notdetected, the offset correction value determined at the time of thepreceding connecting point can be used, so that the disturbance of theservo operation due to the polarity reversal can be avoided. Forinstance, in the case of FIG. 4, the sub-header 5 is detected by the PLLand data detecting circuit 17 and the pattern matching circuit 18, andthe offset due to the push-pull sensor is corrected by the trackingerror signal due to the wobble pits. In addition, the connecting pointdetecting circuit 19 detects whether the sector in question is at aconnecting point, and if the sector is found to be at a connectingpoint, the sample-hold circuit 22 is made to operate at the timing fromthe mirror surface detection circuit 20, and the differential amplifier26 corrects the offset.

If the detection of the mirror surface fails at a connecting pointbecause of a scratch on the disk, for example, then the offset valueheld by the sample-hold circuit 23 one period before is kept used, toensure stable operation. If the detection also failed one period before,the value obtained two periods before is used. To generalize, the valueobtained at the time of the latest successful detection of the mirrorsurface is used. This is because the connecting points are aligned inthe radial direction of the disk, so that the offset ΔTt due to themounting error of the photodetector 11 and the stray light in theoptical head, the offset ΔTi from the photodetector 11 to the polarityreversing circuit 14, and the offset δ due to the tilting of the diskare substantially constant, and because the angle of rotation withrespect to the direction of the eccentricity of the optical disk is alsothe same the offset ΔTg due to the shift of the objective lens is alsosubstantially constant. The correction of offset at the connecting pointvaries substantially compared with the offset at the normal sectors, sothat correction is indispensable.

The system having a correction circuit dedicated to the tracking errorsignal polarity reversal, and using the mirror surface detection is usedin combination with the circuit using wobble pits to perform correctionas shown in FIG. 4. In this case too, by creating a tracking errorsignal from the wobble pits by means of the differential amplifier 27,and adding the tracking error signal from the differential amplifier 27to the original tracking error signal (supplied via the differentialamplifier 16), whereby tracking operation is performed using the wobblepits, free from offset in the low-frequency region as shown in FIG. 28can be achieved. In this case too, the amount of correction of theoffset at the connecting point is large compared with the amount ofcorrection at the normal sectors, so that offset due to the mirrorsurface alone is extracted, and used for feed-forward correction. Thecorrection loop using the wobble pits is not accompanied with a rapidchange even when tracking error signal polarity reversal is effected,and but with a slow change which can be corrected by a control loophaving the gain G2 in FIG. 28.

In the above-described correction, the address pits in the sub-header 5shown in FIG. 5 are reproduced, and the pattern matching signal isgenerated on the basis of the reproduced address data 31, and thepolarity reversing circuit 14 is operates to reverse the polarity of thesignal in accordance with this signal. Then, responsive to the patternmatching signal and the sample-hold timing signal generated, thetracking error signal at the time of the passage of the mirror surfaceis sampled and held.

Such offset correction is effected even for the disk shown in FIG. 1A inwhich the lands and grooves are not connected so that no polarityreversal is required. This is because the push-pull tracking errordetection system has an offset due to the lens shift. When theabove-described offset correction and polarity reversal are erroneous,failure in tracking might occur, and the reproduction of the entiresector is affected.

Accordingly, as shown in FIG. 5, the recognition pattern 30 is made ofpits longer in the track linear direction than the normal address pits,and of a pattern which is not used in the modulation method of theaddress pits and recorded and reproduced data. In this way, distinctionbetween the normal data and recognition data is facilitated, and theconfiguration of the pattern matching circuit can be simplified.

In recent years, block coding is used as modulation for recording andreproducing information. In this case, a ROM table for converting 8 bitdata into 16 bit data, for instance, is provided, and such a combinationof pit patterns that make the minimum and maximum reversal intervalssatisfy a predetermined condition, and reduce variation in DSV (DigitalSum Value) is selected, and the selected combination is recorded in theROM. In this way, encoding is enabled. By performing the above operationin the reverse order, decoding is enabled. In such block modulationsystem, there are a combination of patterns which are not contained inthe above modulation pattern. Such patterns are used as the recognitionpatterns 30, so that it is possible to separate the recognition pattern30 from other information recording data, for the purpose of the patternmatching. Moreover, by using the sequence of pits elongated in the disklinear direction (for instance, the minimum pit length is longer thanthe pits in the information recording part), the error rate at the timeof detection of the recognition flag can be reduced.

If the recognition pattern 30 is different from one zone to another, asshown in FIG. 7, it is possible to determine, by scanning therecognition pattern 30, which zone the light spot is scanning in, and touse this information for the rotational control over the disk motor 9.For instance, if the rotational speed were incorrect in scanning a diskof a phase-change type which has a strong linear velocity dependency,the recording characteristic with regard to the laser power and thelinear velocity would not match, and the over-writing and otherrecording information will not be successful. For this reason, the zonemust be identified without fail. In the case shown in FIG. 7, there arethree zones A, B and C, but there can be a different number of zones. Asimple way is to provide as many number of recognition patterns 30 asthe number of zones. If, however, it is difficult to provide as manynumber of recognition patterns 30 as the number of the zones, becausethe number of the zones is large and/or the number of pits for therecognition patterns 30 is limited, the arrangement may be such that thesame recognition patterns may be used for different zones separated byone or more zones identified by different recognition patterns. Forinstance, if there are only three different recognition patterns, theymay be used in turn, in the order of A, B, C, A, B, C, . . . In thiscase, in the case of a track jump from a first zone to a second zone,separated from the first zone by other zones, the rotational speed inthe first zone (which is scanned before the track jump) is stored, therecognition patterns of the zones across which the track jump iseffected are detected, and the number of repetitions of the recognitionpatterns during the track jump is counted. In this way, the second zoneto which the track jump should be effected can be identified.

If, as shown in FIG. 10, an ID is described as part of the recognitionpattern 30, the reliability of the detection of the recognition pattern30 is further enhanced. For instance, where a plurality of recognitionpatterns 30 are provided in each sub-header 5, or where a plurality ofsub-headers 5 are provided, different ID's 33 may be described. Byreading the ID, the position of the recognition pattern 30 within theheader 6 can be identified, and on the basis thereof, it is alsopossible to identify the timing of detection of the wobble pits, mirrorsurface part 35 in FIG. 10, or mirror surface part 7 in FIG. 3, or theposition at which data recording begins.

By comparing the ID's 33 in a plurality of recognition patterns 30 thathave been reproduced, it can be re-confirmed that the reproduced data isthat of a recognition pattern. For this reason, the reliability isimproved. For instance, if it is checked whether reproduced ID's 33 aresequentially incremented, a recognition pattern 30 with an ID 33 whichdoes not satisfy the condition of the sequential increment is consideredto be a wrong pattern (not a recognition pattern).

Unlike the case of FIG. 7, the recognition pattern 30 may consists of 4to 2 bytes containing matching pits 32, ID 33, zone identifying part 34,mirror surface part 35, and the like, as shown in FIG. 11 to FIG. 13.

The mirror surface part 35 shown in FIG. 10 and FIG. 11 is used not onlyfor removing the track offset, but also for indicating the start or endof a plurality of matching patterns, and the mirror surface part alsoforms part of the matching pattern.

The recognition pattern 30 can be detected more easily than the normalreproduced data or address information in the header part 6. Moreover,because the configuration is such as to ensure reliability, therecognition pattern may be made to contain information which isessential during land/groove recording, so as to ensure correct trackingand rotation control.

Embodiment 2

Determination as to whether the light spot is scanning a land or agroove can be achieved by reading the address data. For instance, if thedisk is divided into annular zones and the number of sectors perrevolution is constant in each zone, by reading the disk address, it ispossible to determine whether the header part the light spot is scanningis at at connecting point from the sector number within the zone. Forinstance, if the number of sectors per revolution within a certain zoneis m, and the sector with a number “0” is at a first connecting point(within the zone), the other connecting points are at the sectors withthe number m×n (n being an integer). Accordingly, by detecting anddecoding the sector address, the fundamental information such as whetherthe light spot is scanning a land or a groove can be obtained.

However, because of reading error during address data reproduction, therecognition of the above-mentioned fundamental information can beerroneous. Therefore, even if the current address cannot be read, sincethe addresses are sequentially incremented by one, by reading theaddresses at one or more preceding sectors, the current address can bepredicted and erroneous reading of the current address can be corrected.However, during initial track pull-in or pull-in after track access,identification must be achieved solely from the data in the header partfor each sector. Moreover, it is desirable that the above-mentionedfundamental information can be read even if the tracking servo is notapplied. If the recognition pattern 30 can be read in the state in whichthe focus is ON, it is possible to effect rotation control promptly, anda normal track crossing signal can be produced even with a disk havinglands and grooves alternating every revolution.

In a disk in which lands and grooves alternate every revolution, it isnecessary to determine whether the header part being scanned is at aconnecting point. If, because of a scratch on the disk, for instance, anunnecessary polarity reversal is effected, failure of tracking mayoccur. Accordingly, it is essential to determine whether the header partbeing scanned is at a connecting point.

In an optical disk capable of re-writing, one-beam tracking is normallyused, so that wobble pits and mirror surface part are provided foroffset detection, and it is important to detect the timing for readingthe wobble pits or mirror surface part. The detection of the offsettiming and the determination as to whether the header part is at aconnecting point must be achieved without fail even if there is atracking deviation. The correction of the tracking deviation should beeffected even when there is a track offset, and therefore thereproduction of the recognition pattern 30 must be achieved without faileven if there is a certain amount of track deviation. If the detectionis achieved even if tracking is not achieved, the servo-pull-in and thelike can be effected.

For this reason, as shown in FIG. 5, FIG. 6 and FIG. 9, a pair ofrecognition patterns 30 are provided, one after another in the trackdirection, and being shifted in the radial direction. That is, the firstrecognition pattern 30 of the pair is aligned with the rest of the pitsin the subheader 5, while the second recognition pattern 30 is shiftedradially outward (downward in the drawings) by one track pitch. Becausethe headers are radially aligned with each other within each zone, asshown in FIG. 2, the recognition patterns 30 are also radially alignedbetween successive tracks within each zone, as shown in FIG. 14.Therefore, if the successive recognition patterns 30 within eachsubheader 5 are shifted in the radial direction (laterally of thetrack), even when the tracking is deviated during reproduction and thelight spot is deviated radially inward or radially outward, there is ahigher probability that at least one of the recognition patterns 30within one sub-header 5 can be reproduced.

In particular, since the address pits in the subheaders 5 are disposed,being shifted by about half a track pitch with respect to theinformation track, if the light spot is deviated toward one side of thetrack, pits on the other side are not reproduced. As a result,land/groove identification and removal of offset cannot be made.However, if the pair of recognition patterns are disposed, being shiftedin the radial direction, as described above, one of the recognitionpatterns in the pair can be reproduced.

Moreover, in a state in which tracking is not applied, the scanning ofthe light spot is as shown in FIG. 14, so that the reproduction ispossible, and reproduction is facilitated because of the above-describedshifting of the recognition patterns.

However, where the recognition patterns 30 are disposed at equalintervals as shown in FIG. 14, if in a state in which tracking is notapplied, the light spot scans along a trace β in the drawing, therecognition patterns 30 in the second and fourth sub-headers 5 (ascounted from the left end) can be reproduced, while if the light spotscans along a trace α, none of the recognition patterns may bereproduced. The probability that the light spot scans along trajectory αmay be sufficiently low. But because failure of reproduction of therecognition pattern 30 leads to the track counting error, or failure inservo-pull-in, it is desired that the cause for failure should beremoved.

For this reason, it may be so arranged that the interval betweenrecognition patterns 30 is not constant. For instance, a mirror surfacepart 7 may be disposed between sub-headers 5, as shown in FIG. 15. Inthis case, when the light spot follows a trace α, the recognitionpatterns 30 in the third and fourth sub-headers 5 as counted from theleft end can be reproduced. When the light spot follows a trace β, therecognition patterns 30 in the second and fourth subheaders 5 as countedfrom the left end can be reproduced.

As an alternative (for making the interval between the recognitionpatterns 30 to be not constant), the length of the VFO 29 may bechanged, as shown in FIG. 15B. In this case, the interval between thesecond and third sub-headers 5 as counted from the left end may beincreased, and also the interval between the third and fourth subheaders5 may be changed, so as to improve the probability of detection. Theprobability of detection of the recognition patterns 30 can be furtherimproved by increasing the number of recognition patterns inserted ineach subheader 5, from two as shown in FIG. 15, to, for example, threeor four.

In the state in which tracking servo is not applied, the recognitionpatterns 30 can be reproduced, and the information indicating the zonecan be obtained. As a result, the rotation control during access isenabled.

Moreover, by reading the recognition patterns, the timing for detectingthe mirror surface part 7 can be obtained. Accordingly, the track offsetcan be removed during track access or before servo pull-in, so that thepull-in can be effected smoothly (pull-in with zero offset is possible).

In general, the light spot is led to the target sector during trackaccess, by calculating the number of tracks to the target sector, andcounting the number of waves of the tracking error signal (indicatingthe number of tracks crossed). During track crossing movement, the trackcrossing speed (speed of radial movement of the light spot) can becalculated from the waveform of the tracking error signal, and used tocontrol the track crossing speed. Moreover, the sum signal indicatingthe amount of reflected light can be used to subtract the reverse-swingcomponent due to the eccentricity of the disk to achieve accuratecounting.

With the optical disk shown in FIG. 1A in which the lands and groovesalternate every revolution, the polarity of the tracking error signal isreversed every revolution, and the tracking error signal 53 shown inFIG. 16 is obtained. If the track counting is effected using this signalas is, track count errs at the connecting point, or, if the light spotis nearing the target sector, the light spot may be pulled into anadjacent track because of the difference in the tracking polarity. As acountermeasure, the timing of polarity reversal 56 is calculated fromthe signal 55 indicative of the recognition patterns, obtained from thereproduced envelope 54, and the original tracking signal 53 can beconverted into a correct tracking error signal 57. With thisarrangement, the track pull-in can be effected stably, and the trackcount can be achieved accurately.

The optical disk drive device for reproducing the recognition patterns30 before tracking or during track access is configured as shown in FIG.17 or FIG. 18. The configuration shown in FIG. 17 includes a zoneidentifying circuit 58 and a rotation control circuit 59, and performsrotation control in a state in which the light spot is not tracking. Theintermittent reproduced envelope signal 54 obtained while the light spotis crossing the tracks is passed through the PLL and data detectingcircuit 17, to the pattern matching circuit 18, which recognizes therecognition pattern 30, and on the basis of the identified zonedescribed by the recognition pattern 30, the zone identifying circuit 48gives an instruction designating the rotation speed to the rotationcontrol circuit 59. With such an arrangement, it is possible to performrotation control even during track access, so that the time required forsettling can be shortened. Similar operation is performed during trackpull-in.

The configuration shown in FIG. 18 is used in combination with a diskshown in FIG. 1B to reverse the tracking polarity every revolution. Itincludes a linear motor 60, tracking polarity identifying circuit 61, atrack count circuit 62, and a feed control circuit 63. The reproducedenvelope signal during the track crossing, obtained at the output of theadder 15 is passed through the PLL and data detecting circuit 17 to thepattern matching circuit 18 which recognizes the recognition pattern 30.Further, the tracking polarity information contained in the recognitionpattern 30 is read by the tracking polarity identifying circuit 61, andis used to control the polarity reversing circuit 14, which therebyperform the reversal of the polarity of the tracking error signal. Onthe basis of the tracking error signal 57 that has been corrected, i.e.,that has its polarity reversed by the reversing circuit 14, track countis performed, and the result of the track count is sent to the feedcontrol circuit 63, which thereby performs the feed control over thelinear motor 60.

In a state in which tracking is not applied, it is possible to correcttrack offset as shown in FIG. 4, and if the track offset is corrected inthe manner shown in FIG. 4, the track counting can be achieved moreaccurately. The reason is explained below. During track access,acceleration is exerted to the objective lens, and the position of theobjective lens is shifted from the center of the actuator, and sensoroffset due to the objective lens shifting occurs, as described inconnection with the prior art. For this reason, there may be a shiftfrom the reference voltage required for binarization for the purpose ofcounting the tracking error signal, and the binarization may not besuccessfully effected. For this reason, the circuit of FIG. 4 is made tooperate during the track access, and the timing of detection of themirror surface part is obtained from the recognition pattern, and usedfor the correction.

FIG. 19 to FIG. 22 shows the configuration of the pattern matchingcircuit 18. FIG. 19 shows the configuration showing a system including apattern matching circuit 18 utilizing the repetition of the recognitionpattern. It includes shift registers 37 to 40 for receiving thereproduced data in series, pattern matching circuits 41 and 42, an ANDgate 42 determining the logical product of the outputs of the patternmatching circuits 41 and 42, a timing circuit 46 for obtaining timingfor reading wobble pits formed of the subheader 5 itself, sample-holdcircuits 44 and 45 for sampling the sum signal (output of the headamplifier 36) when the light spot scans the respective wobble pits, anda differential amplifier 47 determining the difference between theoutputs of the sample-hold circuits 44 and 45.

The configuration shown in FIG. 20 is similar to the that of FIG. 19,but an address ID detecting circuit 48 is added. The address IDdetecting circuit 48 is for performing matching from the ID contained inthe recognition pattern 30. An AND gate 49 determines the logicalproduct of the outputs of the pattern matching circuits 41 and 42, andthe address ID circuit 48.

The configuration shown in FIG. 21 is similar to that of FIG. 20, butthe circuits 40, 42, and 49 are omitted, and a polarity reversingcircuit 50 is added. The configuration performs judgment of therecognition pattern on the basis of whether the recognition patterns 30at the two subheaders 5 out of the four subheaders 5 coincide with eachother.

FIG. 22 is a block diagram showing a pattern matching circuit 18 fordetermining the timing of detection of the mirror surface part bycounting the PLL clock after address ID is detected. It includes n-bitcounter 51, and a sample-hold circuit 52 for holding the tracking errorat the mirror surface part.

With the pattern matching circuit described above, the matching pits 32(FIG. 10, FIG. 11, FIG. 12, FIG. 13) are of a modulated pattern which isnot used for recording data, and judgment is made whether the reproduceddata is identical to that for assigned to the matching pits. However,there is a possibility that erroneous recognition is made because ofscratch or track offset. As a countermeasure, it is possible to improvethe reliability of detection, by utilizing the fact that the recognitionpatterns 30 of the subheader 5 are repeated (if the ID 33 isdisregarded), as shown in FIG. 19. In the circuit shown in FIG. 19, whenboth of the pattern matching circuits 41 and 42 find matching, thetiming for detecting wobble pits is obtained.

The concept of improving the reliability by repeating information canalso be applied to checking whether the reproduced address data iscorrect. However, the recognition pattern 30 contains the mostfundamental information, such as rotation of the motor, trackingpolarity, and must be detected even in a state when the tracking is notapplied. As a result, applying the concept of repeating information ismore important with regard to the recognition pattern 30. Thereliability is further improved, if, in combination with the above, thecorrectness is checked as to the incremented value at the ID 33.

In this case, an address ID detecting circuit 48 shown in FIG. 20 isused to perform matching with a predetermined pattern, such as“00011011.” The pattern matching circuit 41 compares the outputs A and Cof the first and third shift registers 37 and 39, while the patternmatching circuit 42 compares the outputs B and D of the second andfourth shift registers 38 and 40. This is for comparing the subheadersshifted in the same radial direction, i.e., for comparing theradially-outwardly-shifted subheaders with each other, and for comparingthe radially-inwardly-shifted subheaders with each other.

When the pattern matching is effected using only such subheaders 5 thatare shifted in one of the radially inward or outward directions, it issufficient to compare the outputs A and C of the shift registers 37 and39, as shown in FIG. 21. On the basis of the ID 33 detected in thismanner, the timing of detecting the wobble pits is obtained. By settingthe ID in an n-bit counter 51, and PLL clock is counted until the countreaches the set value, to obtain the timing of detection of the wobblepits. However, when the detection of the subheaders 5 is commenced at amiddle, the order of detection of the wobble pits is reversed, so thatthe timing is reversed by the polarity reversing circuit 50 shown inFIG. 21. In this way, a tracking error signal free from offset can beobtained from the sum signal.

The configuration shown in FIG. 22 may be used to perform mirror surfacecorrection in the same way as in FIG. 21. In this case, the output ofthe n-bit counter is connected to the sample-hold circuit 52, and thetracking error signal is sampled at the time of passage of the mirrorsurface part. With such a configuration, even in a state in whichtracking servo is not applied, the recognition patterns 30 can bedetected, and used for correction of offset at the mirror surface part7, or to switch the tracking polarity.

In the system shown in FIG. 21 and FIG. 22 which uses only suchsubheaders 5 that are shifted in one of the radially outward and inwarddirections has a lower reliability than the system shown in FIG. 19, butis suitable in a state in which tracking servo is not applied, or whenthe recognition patterns are not fully obtained.

What is claimed is:
 1. An optical disk having information recordingtracks in the form of land and groove tracks arranged in a land/groovesingle-spiral configuration in which land tracks are connected toadjacent groove tracks at connecting points which occur each revolutionso that land and groove tracks alternate every revolution to form acontinuous spiral; said disk being divided into a plurality of annularzones, each revolution of said information recording track belonging toone of the zones depending on the position of the revolution in theradial direction; each revolution of the information recording trackbeing divided into a plurality of sectors of a unit length ofinformation recording in a scanning direction; said disk having a headerportion at the head of each sector, said header portion including aplurality of recognition patterns which are each formed of a pluralityof pits, said header including a plurality of sub-headers that eachinclude address pits and a recognition pattern formed of a plurality ofpits, a first sub-header of said plurality of sub-headers having addresspits that signify an address of a first sector and a second sub-headerof said plurality of sub-headers having address pits that signify anaddress of a second sector, the address of the second sector beingdifferent than the address of the first sector, the address pits of thefirst sub-header being shifted in a first radial direction from a trackcenter and the address pits of the second sub-header being shifted in asecond radial direction, opposite the first radial direction, from thetrack center; and the interval between the recognition patterns in theheader portion being varied.
 2. The disk according to claim 1, whereinthe interval between recognition patterns is varied by varying thelength of a VFO region.
 3. The disk according to claim 1, wherein saidplurality of pits that form a recognition pattern has a pattern which isnot used to represent data or address information.
 4. The disk accordingto claim 1, wherein a recognition pattern identifies whether the sectoris at a connecting point between a land track and a groove track.
 5. Thedisk according to claim 1, wherein the headers are aligned in the radialdirection.
 6. The disk according to claim 1, wherein said plurality ofsub-headers further includes a third sub-header having address pits thatsignify the address of the first sector and a fourth sub-header havingaddress pits that signify the address of the second sector, the addresspits of the third sub-header being shifted in the first radial directionfrom the track center and the address pits of the fourth sub-headerbeing shifted in the second radial direction from the track center. 7.The disk according to claim 1, wherein the address pits of the firstsub-header are shifted in the first radial direction from the trackcenter by a distance of ½ track pitch and the address pits of the secondsub-header are shifted in the second radial direction from the trackcenter by a distance of ½ track pitch.
 8. The disk according to claim 1,wherein said plurality of sub-headers further includes a thirdsub-header positioned along a track direction between said firstsub-header and said second sub-header and a fourth sub-header positionedalong the track direction after said second sub-header.
 9. The diskaccording to claim 8, wherein an interval between a recognition patternin said first sub-header and a recognition pattern in said thirdsub-header is different than an interval between a recognition patternin said third sub-header and a recognition pattern in said secondsub-header.
 10. The disk according to claim 9, wherein an intervalbetween a recognition pattern in said second sub-header and arecognition pattern in said fourth sub-header is the same as theinterval between a recognition pattern in said first sub-header and arecognition pattern in said third sub-header.